The Tetracyclic Towers are four mysterious towers in Liberl, dating back to before the Great Collapse. They each separately known as the Esmelas Tower, Amberl Tower, Sapphirl Tower and Carnelia Tower and each of them are named after the septium names of wind, earth, water and fire, respectively.
During Trails in the Sky SC, it is revealed that these towers were originally built to seal away the Liber Ark. Epithetically named the Device Towers, they seal the Liber Ark away from its power source, the Aureole in another dimension, forming a second safeguard should the Lakeside facility and Ahnenburg fail. The ancient Liberl civilization constructed the towers after most of its population in the floating city became corrupted by their own technology.
Estelle Bright visits each of the towers on various bracer missions. It is by the Esmelas tower that she first becomes acquainted with Professor Alba. The Esmelas Tower is first reached by Estelle and Joshua on an emergency rescue mission to ensure Luke's and Pat's safety. Later Estelle and Joshua returned to the tower on a escort mission for a reporter, Nial Burns, and his photographer, Dorothy Hyatt. This time they scale the whole tower to the roof where they met an archaeologist, Professor Alba, at the top. Joshua suddenly gets a headache after seeing Alba.
The towers themselves do not play a crucial role until it is revealed that they form an integral part of the second seal on the Aureole. Celeste D. Auslese and her fifteen companions had built the towers under the guise of studying the Septium veins when in truth they were creating a network of devices that would spatially seal the Liber Ark. The cessation of the towers is a necessary part of Georg Weissmann's plan using replica Gospels.
Estelle and company visit each of the towers in a bid to stop the Enforcers, traversing the Altered Space generated by the tower's activation. They ultimately are unsuccessful however and the Second seal collapses, heralding the return of the Liber Ark from its prison dimension.
The four towers are spread throughout Liberl. These towers include:
|Esmelas Tower||Green||Wind||Rolent||Enforcer No. X: Bleublanc|
|Amberl Tower||Yellow||Earth||Bose||Enforcer No. XV: Renne|
|Sapphirl Tower||Blue||Water||Ruan||Enforcer No. VI: Luciola|
|Carnelia Tower||Red||Fire||Zeiss||Enforcer No. VIII: Walter|